1. Field of the Ivention
The present invention relates to the scanning of images such as characters, marks, symbols, graphic images etc. printed on both sides of different kinds of documents, and then converting electrical signals representing such scanned images to digital data.
2. Description of the Prior Art
In order to obtain the image data of characters, graphic images, etc. from both sides of a document read by using an optical scanner, it is common proactice to first read the image data on one side of a document by means of a scanner. Thereafter the image data on the opposite side of the document is read by the scanner.
In this respect, in order for a conventional scanner to acquire the image data from a scanning operation both sides of a document, it would normally take at least twice as long as that required for the aquisition of image data from a single side of a document.
While the simultaneous reading of such image data from both sides of a document would make the scanning operation time shorter, in practice it would require two separate circuits, one for obtaining the image data from one side of an object and another circuit for obtaining data from the other side. As a consequence, such a dual-circuit arrangement would not only bring about a substantial increase in production costs, but also lead to a large-sized construction of a scanning apparatus. In addition, when it is desired to design a machine which can read both sides of a document such as a bank check which has an endorsement on the back thereof, if would be necessary to provide such a machine with the necessary structure for confirming that the images obtained are those taken from both sides of the same document.